Investigating Synergistic Effects of Dermasptin B1 Recombinant Proteins and Peppermint Essential Oils against Gram-negative Phytopathogens Bacteria using Fractional Inhibitory Concentration Index (FIC)

Due to the increasing concern about the growing resistance of pathogenic bacteria to a variety of common antibiotics, it is vital to find and introduce new drugs to treat bacterial infections. To this end, intensive efforts need to be taken to find novel antimicrobial agents with diverse antimicrobial modes of action, preventing pathogen growth. Combination therapy using current antibiotics and other biological or chemical molecules might be efficient as an exciting new approach.

In the present study, the synergistic antibacterial activity of Dermastin B1 recombinant peptides isolated from transgenic T1 tobacco plants either alone or in combination with peppermint essential oils were evaluated against Xanthomonas translucen, Xanthomonas perforans, Xanthomonas citri, Xanthomonas gardneri and Pseudomonas syringae by measuring the Fractional Inhibitory Concentration (FIC) index at different concentrations.

The results of this study showed that the MIC of Dermaseptin B1 peptides and the peppermint essential oils against bacteria were 50 µg/ml and 4.6 µg/ml, respectively. FIC index showed a synergistic effect of peppermint essential oils with Dermaseptin B1 recombinant peptide with FIC=0.49.

The results of this study suggest that Dermasptin B1 recombinant peptides can be effective either alone or in combination with the peppermint essential oils to control bacterial infections. However, it seems that there is a synergistic effect between recombinant peptides and peppermint essential oils in combat against phytopathogens.